As a high dielectric constant insulating film used for a gate insulating film of a field-effect transistor such as a MOSFET and the like or a capacity insulating film of a capacitor, an insulating film having higher dielectric constant is required, which is alternative to a silicate oxide film (SiO2 film) and a silicon oxynitride film (SiON film).
As the above high dielectric constant insulating film, a study concerning an insulating film containing a rare earth metal has been made. An M2O3 film having a simple composition in which the rare earth metal is denoted as “M” is thermally and chemically labile, so that it cannot be used as it is.
Hence, a MOSFET including a multilayer oxide film structure is devised, in which a thin SiO2 film having a good interface state between a silicon substrate and itself is provided on the silicon substrate, and in which a high dielectric constant metal oxide film is formed thereon. In addition, it is proposed that a rare-earth metal oxide film is formed as such metal oxide film.
However, in the multilayer oxide film structure as described above, if a film-forming is performed in a low temperature and a test is performed in a low temperature, an adequate result could be obtained, however, such structure cannot actually be applied to a semiconductor device.
In other words, when an electron device containing various silicon materials is manufactured, high-temperature heat treatments at 600° C. to 1050° C. are frequently performed especially before a metal wiring is formed. Therefore, the high dielectric constant insulating film is required to have tolerance to the high-temperature heat treatment. However, if the high-temperature heat treatment is performed to the aforementioned multilayer oxide film structure, the properties vary during the heat treatment. As a result, problems such as, for example, a deterioration of the interface state and a decrease of the dielectric constant occur.
Patent document 1
Japanese Patent Application Laid-open No. 2002-324901
Patent document 2
Japanese Patent Application Laid-open No. 2002-184773
Patent document 3
Japanese Patent Application Laid-open No. 2002-329847